Helictite
Encyclopedia
A helictite is a speleothem
found in limestone
cave
s that changes its axis from the vertical at one or more stages during its growth. They have a curving or angular form that looks as if they were grown in zero gravity. They are most likely the result of capillary forces
acting on tiny water droplets, a force often strong enough at this scale to defy gravity.
Helictites are, perhaps, the most delicate of cave formations. They are usually made of needle-form calcite
and aragonite
. Forms of helictites have been described in several types: ribbon helictites, saws, rods, butterflies, "hands", curly-fries, and "clumps of worms." They typically have radial symmetry. They can be easily crushed or broken by the slightest touch. Because of this, helictites are rarely seen within arm's reach in tourist
caves.
Timpanogos Cave National Monument
in Utah has one of the largest collections of these formations in the world.
are blown to one side, so the dripstone grows in that direction. If the wind changes, the direction of growth changes too. However this theory is very problematic, because wind directions change very often. The wind in caves depends on air pressure changes outside, which in turn depend on the weather. Wind caves are known to experience these windy conditions. The wind direction changes as often as the weather conditions outside change. But the dripstones grow very slowly - several centimeters in 100 years - meaning the wind direction would have to stay steady for long periods of time, changing for every fragment of a millimeter of growth. A second problem with this theory is that many caves with helictites have no natural entrance where wind could enter.
For an unknown reason, when the chemical composition of the water is slightly altered, the single crystal structure can change from a cylindrical shape to a conical one. In some of these cases, each crystal fits into the prior one like an inverted stack of ice cream cones.
Speleothem
A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...
found in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
s that changes its axis from the vertical at one or more stages during its growth. They have a curving or angular form that looks as if they were grown in zero gravity. They are most likely the result of capillary forces
Capillary action
Capillary action, or capilarity, is the ability of a liquid to flow against gravity where liquid spontanously rise in a narrow space such as between the hair of a paint-brush, in a thin tube, or in porous material such as paper or in some non-porous material such as liquified carbon fiber, or in a...
acting on tiny water droplets, a force often strong enough at this scale to defy gravity.
Helictites are, perhaps, the most delicate of cave formations. They are usually made of needle-form calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
and aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
. Forms of helictites have been described in several types: ribbon helictites, saws, rods, butterflies, "hands", curly-fries, and "clumps of worms." They typically have radial symmetry. They can be easily crushed or broken by the slightest touch. Because of this, helictites are rarely seen within arm's reach in tourist
Tourism
Tourism is travel for recreational, leisure or business purposes. The World Tourism Organization defines tourists as people "traveling to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes".Tourism has become a...
caves.
Timpanogos Cave National Monument
Timpanogos Cave National Monument
Timpanogos Cave National Monument is a cave system in the Wasatch mountains in American Fork Canyon near American Fork, Utah, in the United States. The 1.5 mile trail to the cave is steep at several points, but paved and wide, so the cave opening is accessible to most...
in Utah has one of the largest collections of these formations in the world.
Formation
The growth of helictites is still quite enigmatic. Until now, there has been no satisfactory explanation for how they are formed. Currently, formation by capillary forces is the most likely theory, but another theory based on wind formation is also viable.Capillary forces
The most likely theory explains helictites as a result of capillary forces. If the helictite has a very thin central tube where the water flows like it does in straws, capillary forces would be able to transport water against gravity. This theory was inspired by some hollow helictites. However, the majority of helictites are definitely not hollow. Despite this, droplets can be drawn to the tips of existing structures and deposit their calcite load almost anywhere thereon. This can lead to the wandering and curling structures seen in many helictites.Wind
Another theory names the wind in the cave as main reason for the strange look. Drops hanging on a stalactiteStalactite
A stalactite , "to drip", and meaning "that which drips") is a type of speleothem that hangs from the ceiling of limestone caves. It is a type of dripstone...
are blown to one side, so the dripstone grows in that direction. If the wind changes, the direction of growth changes too. However this theory is very problematic, because wind directions change very often. The wind in caves depends on air pressure changes outside, which in turn depend on the weather. Wind caves are known to experience these windy conditions. The wind direction changes as often as the weather conditions outside change. But the dripstones grow very slowly - several centimeters in 100 years - meaning the wind direction would have to stay steady for long periods of time, changing for every fragment of a millimeter of growth. A second problem with this theory is that many caves with helictites have no natural entrance where wind could enter.
Piezo Electric Forces
A theory is proposed that slowly changing geological pressure causing stresses on the crystals at the base alters the piezo electrostatic potential and causes particle deposition to be oriented in some relationship to the prevailing pressure orientation.Helictite growth
A helictite starts its growth as a tiny stalactite. The direction of the end of the straw may wander, twist like a corkscrew, or the main part may form normally while small helictites pop out of its side like rootlets or fishhooks. In some caves, helictites cluster together and form bushes as large as six feet tall. These bushes grow from the floor of the cave. When helictites are found on cave floors, they are referred to as heligmites, though there is debate as to whether this is a genuine subcategory.For an unknown reason, when the chemical composition of the water is slightly altered, the single crystal structure can change from a cylindrical shape to a conical one. In some of these cases, each crystal fits into the prior one like an inverted stack of ice cream cones.